Cg. Ponte et al., BOVINE SERUM-ALBUMIN POTENTIATES CAFFEINE-INDUCED OR ATP-INDUCED TENSION IN HUMAN SKINNED SKELETAL-MUSCLE FIBERS, Brazilian journal of medical and biological research, 30(5), 1997, pp. 675-678
Human skinned muscle fibers were used to investigate the effects of bo
vine serum albumin (BSA) on the tension/pCa relationship and on the fu
nctional properties of the Ca2+-release channel of the sarcoplasmic re
ticulum (SR). In both fast- and slow-type fibers, identified by their
tension response to pSr 5.0, BSA (0.7-15 mu M) had no effect on the Ca
2+ affinity of the contractile proteins and elicited no tension per se
in Ca2+-loaded fibers. In contrast, BSA (>1.0 mu M) potentiated the c
affeine-induced tension in Ca2+-loaded fibers, this effect being more
intense in slow-type fibers. Thus, BSA reduced the threshold caffeine
concentration required for eliciting detectable tension, and increased
the amplitude, the rate of rise and the area under the curve of caffe
ine-induced tension. BSA also potentiated the tension elicited in Ca2-loaded fibers by low-Mg2+ solutions containing 1.0 mM free ATP. These
results suggest that BSA modulates the response of the human skeletal
muscle SR Ca2+-release channel to activators such as caffeine and ATP
.